Traffic sits at a stop light under the West Park Tollway near the Southwest Freeway, Wednesday, Aug. 28, 2013, in Houston. Environmental regulators and scientists don't know how all those idling cars and trucks affect the health of those living and working near the freeways. Starting in January, the Texas Commission on Environmental Quality will begin measuring air pollution levels along the busy stretch of the 59. The federal government required the monitors, which will provide the state with its first data on the health risks within 300 feet of freeways. (Cody Duty / Houston Chronicle)

Traffic sits at a stop light under the West Park Tollway near the...

The traffic is bad in Houston. That's clear to anyone who drives in this congested metropolis. What isn't known is how all those idling cars and trucks affect the health of those living near the freeways.

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